Epoxy resin compositions for encapsulating semiconductors, and semiconductor devices

ABSTRACT

An epoxy resin composition for sealing semiconductors which does not contain any halogen compounds or antimony compounds, has an excellent flame retarding property and shows excellent high temperatures storage life and reliability in a humid condition, and a semiconductor device are provided. The epoxy resin composition for sealing semiconductors comprises (A) an epoxy resin, (B) a phenol resin curing agents, (C) a curing accelerator, (D) an inorganic filler and (E) zinc molybdate as the essential components and the semiconductor device is sealed with this epoxy resin composition.

TECHNICAL FIELD

The present invention relates to an epoxy resin composition for sealingsemiconductors and a semiconductor device. More particularly, thepresent invention relates to an epoxy resin composition for sealingsemiconductors which does not contain any halogen fire retardants orantimony fire retardants and shows excellent high temperatures storagelife, flame retarding property and reliability in a humid condition, andto a semiconductor device using this epoxy resin composition.

BACKGROUND ART

Heretofore, electronic parts such as diodes, transistors and integratedcircuits are sealed mainly with epoxy resin compositions. The epoxyresin compositions contain fire retardants containing a halogen and anantimony compound to provide the composition with the flame retardingproperty. The flame retarding property of the composition is exhibitedby generation of a gas of a halogen or an antimony halide at hightemperatures.

However, in accordance with the above method for exhibiting the flameretarding property, a gas of a halogen or an antimony halide isgenerated when an electronic part is exposed to a high temperature andthis causes a big problem in that corrosion of aluminum circuits andfracture of connecting portions between aluminum pads and gold wires inchips take place. Moreover, it is required for protection of theenvironment and the health that an epoxy resin composition which doesnot use any fire retardants containing a halogen or an antimony compoundand exhibits an excellent flame retarding property be developed.

To overcome the above problems, a resin composition having a glasstransition temperature higher than the temperature of the environmentwhich is obtained by a combination of an epoxy resin and a phenol resincuring agent is used to decrease diffusion of a gas of a halogen or anantimony halide during storage at high temperatures and hightemperatures storage life can be improved. Alternatively, an ionscavenger may be added to scavenge gases of a halogen or an antimonyhalide generated during storage at high temperatures. A combination ofthese methods may also be used.

On the other hand, recently, electronic parts are often disposed at thesurface of substrates of circuits. The size of electronic parts arebecoming smaller and thinner. Therefore, improvement in crack resistanceis required in soldering for attachment of electronic parts tosubstrates of circuits. Thus, an epoxy resin composition exhibiting bothof excellent crack resistance in soldering and excellent hightemperatures storage life has been desired. However, even when an epoxyresin composition which contains a fire retardant of a halogen compoundor a combination of a halogen compound and an antimony compound andexhibits excellent crack resistance in soldering is used, addition of anion scavenger cannot provide sufficient high temperatures storage lifewhen the epoxy resin composition has a low glass transition temperature.On the other hand, an epoxy resin composition shows insufficient crackresistance in soldering when the epoxy composition has a high glasstransition temperature. No epoxy resin compositions which have a lowglass transition temperature and exhibit excellent high temperaturesstorage life have been provided.

Various fire retardants other than fire retardants containing a halogenand antimony compounds have been studied. For example, metal hydroxidessuch as aluminum hydroxide and magnesium hydroxide and boron compoundshave been studied. However, these compounds do not effectively exhibitthe flame retarding property unless they are used in a large amount.Moreover, these compounds contain large amounts of impurities andreliability in a humid condition is not satisfactory. Therefore, thesecompounds are not practically used. Fire retardants containing redphosphorus are effective even when these fire retardants are used insmall amounts and are useful for fire retardation of epoxy resincompositions. However, red phosphorus has a problem in reliability in ahumid condition because red phosphorus reacts with a minute amount ofwater to form phosphines and corrosive phosphoric acid. An epoxy resincomposition which exhibits both of the flame retarding property and thereliability in a humid condition without using a fire retardantcontaining a halogen or an antimony compound has been desired.

The present invention has an object to provide an epoxy resincomposition for sealing semiconductors which does not contain anyhalogen compounds or antimony compounds, has an excellent flameretarding property and exhibits excellent high temperatures storage lifeand reliability in a humid condition, and to provide a semiconductordevice using this epoxy resin composition.

DISCLOSURE OF THE INVENTION

As the result of extensive studies by the present inventors to achievethe above object, it was found that the long term reliability of anepoxy resin composition in a humid condition can be remarkably improvedby using zinc molybdate without deterioration in the flame retardingproperty. The present invention has been completed on the basis of thisknowledge.

Accordingly, the present invention provides:

(1) An epoxy resin composition for sealing semiconductors whichcomprises (A) an epoxy resin, (B) a phenol resin curing agent, (C) acuring accelerator, (D) an inorganic filler and (E) zinc molybdate asessential components;

(2) An epoxy resin composition for sealing semiconductors described in(1), wherein zinc molybdate coats an inorganic substance;

(3) An epoxy resin composition for sealing semiconductors described in(2), wherein the inorganic substance is fused spherical silica;

(4) An epoxy resin composition for sealing semiconductors described inany of (1), (2) and (3), wherein the epoxy resin is a crystalline epoxyresin represented by one of the following formulae [1], [2] and [3]:

 wherein R represents hydrogen atom, a halogen atom or an alkyl grouphaving 1 to 12 carbon atoms and the plurality of R may be the same withor different from each other;

(5) An epoxy resin composition for sealing semiconductors described inany of (1), (2), (3) and (4), which further comprises an ion scavengerrepresented by one of the following formulae [4], [5] and [6]:

BiO_(a)(OH)_(b)(NO₃)_(c)  [4]

wherein a=0.9 to 1.1, b=0.6 to 0.8 and c=0 to 0.4

BiO_(d)(OH)_(e)(NO₃)_(f)(HSiO₃)_(g)  [5]

wherein d=0.9 to 1.1, e=0.6 to 0.8 and f+g=0.2 to 0.4

Mg_(h)Al_(i)(OH)_(2h+3i−2k)(CO₃)_(k)·mH₂O  [6]

wherein 0<j/h≦1, 0≦k/j<1.5 and m represents a positive number; and

(6) A semiconductor device sealed with an epoxy resin composition forsealing semiconductors described in any of (1), (2), (3), (4) and (5).

THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION

The epoxy resin composition for sealing semiconductors of the presentinvention comprises (A) an epoxy resin, (B) a phenol resin curingagents, (C) a curing accelerator, (D) an inorganic filler and (E) zincmolybdate as the essential components.

The epoxy resin of component (A) used in the composition of the presentinvention is not particularly limited and a monomer, an oligomer or apolymer having two or more epoxy groups in one molecule can be used.Examples of the epoxy resin include epoxy resins derived from bisphenolA, epoxy resins containing bromine, epoxy resins derived from bisphenolF, epoxy resins derived from bisphenol AD, epoxy resins derived frombiphenyl, epoxy resins derived from hydroquinone, epoxy resins derivedfrom stilbene, epoxy resins derived from phenol novolaks, epoxy resinsderived from cresol novolaks, epoxy resins derived fromtriphenolmethane, epoxy resins derived from triphenolmethane andmodified with alkyl groups, epoxy resins containing triazine cores,epoxy resins derived from phenol and modified with dicyclopentadiene,cyclic aliphatic epoxy resins, epoxy resins derived from glycidylesters, epoxy resins derived from glycidylamines and heterocyclic epoxyresins. These epoxy resins may be used singly or as a combination of twoor more types.

Among these epoxy resins, crystalline epoxy resins derived frombiphenyl, hydroquinone or stilbene which are represented by thefollowing formula [1], [2] or [3], respectively, can be preferably used:

In the above formulae, R represents hydrogen atom, a halogen atom or analkyl group having 1 to 12 carbon atoms and the plurality of R may bethe same with or different from each other. The crystalline epoxy resinsrepresented by formula [1], [2] or [3] have low viscosity and can bemixed with a large amount of inorganic fillers such as silica.Therefore, the resin composition comprising the epoxy resin showsexcellent crack resistance in soldering. On the other hand, the glasstransition temperature of a cured composition decreases and hightemperatures storage life becomes inferior. However, the hightemperatures storage life can be improved by using zinc molybdate inaccordance with the present invention. Thus, excellent crack resistancein soldering and excellent high temperatures storage life can beachieved.

The phenol resin curing agent of component (B) used in the compositionof the present invention is not particularly limited and a monomer, anoligomer or a polymer having two or more phenolic hydroxyl group in onemolecule can be used. Examples of the phenol resin curing agent includephenol novolak resins, cresol novolak resins, phenol resins modifiedwith dicyclopentadiene, phenol resins modified with xylylene, phenolresins modified with terpene and novolak resins derived fromtriphenolmethane. The phenol resin curing agents may be used singly oras a combination of two or more types. Among these phenol resin curingagents, phenol novolak resin, phenol resins modified withdicyclopentadiene, phenol resins modified with xylylene and phenolresins modified with terpene can be preferably used. The phenol resincuring agent is preferably used in an amount such that the ratio of thenumber of epoxy group in the epoxy resin and the number of phenolichydroxyl group in the phenol resin curing agent is 0.8 to 1.3 in theresin composition.

The curing accelerator of component (C) used in the composition of thepresent invention is not particularly limited. Examples of the curingaccelerator include curing accelerators of amines, curing acceleratorsof polyaminoamides, curing accelerators of acid anhydrides, basic activehydrogen compounds, curing accelerators containing phosphorus andimidazoles. The curing accelerators may be used singly or as acombination of two or more types. Among these curing accelerators,1,8-diazabicyclo[5,4,0]undecene-7, triphenylphosphine and2-methylimidazole are preferably used.

The inorganic filler of component (D) used in the composition of thepresent invention is not particularly limited. Examples of the inorganicfiller include powder of fused silica, powder of crystalline silica,alumina and silicon nitride. The inorganic filler may be used singly oras a combination of two or more types. The amount of the inorganicfiller is not particularly limited. When the balance between moldabilityand crack resistance in soldering is taken into consideration, it ispreferable that the inorganic filler is used in an amount of 60 to 95%by weight of the total amount of the epoxy resin composition. When theamount of the inorganic filler is less than 60% by weight of the totalamount of the epoxy resin composition, there is the possibility that thecrack resistance in soldering becomes inferior due to an increase inabsorption of moisture. When the amount of the inorganic filler exceeds95% by weight of the total amount of the epoxy resin composition, thereis the possibility that problems occur during molding such as wire sweepand pad shift.

The epoxy resin composition for sealing semiconductors of the presentinvention comprises zinc molybdate of component (E). In the compositionof the present invention, zinc molybdate works as the fire retardant. Byusing zinc molybdate, the flame retarding property of the semiconductordevice sealed with the resin composition comprising zinc molybdate ismaintained and the long term reliability of the device in a humidcondition is remarkably improved. It has been known that zinc molybdateis effective as an agent for suppressing smoke and as a fire retardantfor vinyl chloride resins. However, zinc molybdate has never beenapplied to any materials for sealing semiconductors. It is known thatzinc molybdate accelerates carbonation of components of cured resins.Therefore, the mechanism of fire retardation by zinc molybdate can beconsidered as follows: accelerated carbonation during burning suppressescontact of oxygen in the air with the composition and burning is stoppedto achieve the fire retardation.

In the composition of the present invention, zinc molybdate may be usedalone. However, it is preferable that zinc molybdate is used in the formcoating an inorganic substance. Zinc molybdate has the tendency toabsorb moisture. When zinc molybdate is used in a large amount,absorption of moisture by a semiconductor device increases and there isthe possibility that crack resistance in soldering and reliability in ahumid condition deteriorate. Therefore, it is preferable that aninorganic substance such as a transition metal, fused spherical silica,fused crushed silica, alumina clay, talc, zinc oxide, calcium carbonate,aluminum nitride, silicon nitride, aluminum silicate and magnesiumsilicate is used as a core material and the core material is coated withzinc molybdate. By using zinc molybdate in the form coating theinorganic substance, zinc molybdate at the surface alone works as thefire retardant and an increase in absorption of moisture by an increasein the amount of zinc molybdate can be suppressed.

Silica can be preferably used as the inorganic substance which is coatedwith zinc molybdate. Silica contains little impurities and there is nopossibility that reliability in a humid condition deteriorates due tosilica even when coating of silica with zinc molybdate is insufficient.Silica used herein is not particularly limited and any of crystallinesilica and amorphous silica can be used. It is preferable that fusedspherical silica is used. Addition of zinc molybdate in the form coatingthe core material of fused silica does not adversely affect variousproperties such as fluidity of the resin composition and mechanicalstrength of a cured product because fused spherical silica itself hasexcellent fluidity.

In the composition of the present invention, the amount of zincmolybdate coating fused spherical silica is preferably 5 to 40% byweight of the total amount of fused spherical silica and zinc molybdate.Particles obtained by coating fused spherical silica with zinc molybdatepreferably have an average diameter of 0.5 to 50 μm and the maximumdiameter of 100 μm or less. The content of zinc molybdate in the epoxyresin composition is preferably 0.05 to 20% by weight and morepreferably 0.5 to 10% by weight of the total amount of the epoxy resincomposition. When the content is less than 0.05% by weight, there is thepossibility that a sufficient flame retarding property cannot beobtained. When the content exceeds 20% by weight, the amount of ionicimpurities in the epoxy resin composition increases and there is thepossibility that reliability in a humid condition, for example, in thecondition of the pressure cooker test, becomes insufficient.

The process for coating fused spherical silica with zinc molybdate isnot particularly limited. For example, fused spherical silica coatedwith zinc molybdate can be obtained in accordance with the followingprocess: Molybdenum oxide and fused spherical silica are mixed togetherin water to prepare a slurry. The prepared slurry is heated at 70° C.and a slurry containing zinc oxide is slowly added to the heated slurryand mixed. The obtained mixture is stirred for about one hour. Then, theproduct is filtered to separate solid components. Water is removed fromthe solid components and the obtained product is pulverized. Afterincineration at 550° C. for 8 hours, fused spherical silica coated withzinc molybdate can be obtained. Inorganic substances coated with zincmolybdate are also commercially available, for example, from SHERWINWILLIAMS Company.

In the epoxy resin composition for sealing semiconductors of the presentinvention, an ion scavenger can be used. The ion scavenger is notparticularly limited. Compounds represented by one of the followingformulae [4], [5] and [6] can be preferably used:

BiO_(a)(OH)_(b)(NO₃)_(c)  [4]

BiO_(d)(OH)_(e)(NO₃)_(f)(HSiO₃)_(g)  [5]

Mg_(h)Al_(i)(OH)_(2h+3i−2k)(CO₃)_(k)·mH₂O  [6]

In formula [4], a=0.9 to 1.1, b=0.6 to 0.8 and c=0 to 0.4. In formula[5], d=0.9 to 1.1, e=0.6 to 0.8 and f+g=0.2 to 0.4. In formula [6],0<j/h≦1, 0≦k/j<1.5 and m represents a positive number.

Halogen anions and anions of organic acids can be scavenged by using theion scavenger in the composition of the present invention and theamounts of ionic impurities which are brought into the composition withthe resin components can be reduced. The ionic impurities corrodealuminum circuits and pads. The ionic impurities can be scavenged by theion scavenger and corrosion of aluminum can be prevented. The ionscavenger may be used singly or as a combination of two or more types.The amount of the ion scavenger is preferably 0.1 to 5% by weight of thetotal amount of the epoxy resin composition. When the amount of the ionscavenger is less than 0.1% by weight of the total amount of the epoxyresin composition, scavenging of ionic impurities is insufficient andthere is the possibility that reliability in a humid condition in anenvironmental test such as the pressure cooker test becomesinsufficient. When the amount of the ion scavenger exceeds 5% by weightof the total amount of the epoxy resin composition, there is thepossibility that the flame retarding property of the epoxy resincomposition deteriorates.

To the epoxy resin composition for sealing semiconductors of the presentinvention, other additives may be added, where necessary. Examples ofthe other additives include silane coupling agents, coloring agents suchas carbon black and iron oxide red, mold releases such as natural waxesand synthetic waxes and agents for decreasing stress such as siliconeoils and rubber.

The process for producing the composition of the present invention isnot particularly limited. For example, the epoxy resin of component (A),the phenol resin curing agent of component (B), the curing acceleratorof component (C), the inorganic filler of component (D), zinc molybdateof component (E), the ion scavenger of component (F) and other additivesare sufficiently mixed together by using a mixer or the like and thenmelt kneaded by using a heated roll or a kneader. The obtained productis cooled and pulverized. The epoxy resin composition for sealingsemiconductors of the present invention can be applied to coating,insulation and sealing of electric and electronic parts such astransistors and integrated circuits by curing and molding in accordancewith a molding process such as transfer molding, compression molding orinjection molding.

EXAMPLES

The present invention will be described more specifically with referenceto examples in the following. However, the present invention is notlimited to the examples.

Abbreviations and structures of the epoxy resins, the phenol resincuring agents and the ion scavengers used in the examples and thecomparative examples are shown together in the following.

(1) Epoxy Resins Derived from Biphenyl

YX4000K; manufactured by YUKA SHELL EPOXY Co., Ltd.; melting point, 105°C.; epoxy equivalent, 185 g/eq.

(2) Epoxy Resin 1

An epoxy resin expressed by formula [7].

(3) Epoxy Resin 2

An epoxy resin expressed by formula [8].

(4) Epoxy Resin Derived from O-cresol Novolak

Epoxy equivalent, 200 g/eq.

(5) Epoxy Resin 3

An epoxy resin containing a compound having the structure expressed byformula [9] as the main component; epoxy equivalent, 190 g/eq.

(6) Epoxy Resin 4

A mixture of 60% by weight of a resin containing a compound having thestructure expressed by formula [10] as the main component and 40% byweight of a resin containing a compound having the structure expressedby formula [11] as the main component; epoxy equivalent, 210 g/eq.

(7) Epoxy Resin 5

An epoxy resin containing a compound having the structure expressed byformula [12]; epoxy equivalent, 260 g/eq.

(8) Epoxy Resin 6

An epoxy resin containing a compound having the structure expressed byformula [13]; epoxy equivalent, 274 g/eq.

(9) Phenol Novolak Resin

Softening point, 95° C.; hydroxyl equivalent, 104 g/eq.

(10) Phenol Resin 1

A phenol resin expressed by formula [14]; hydroxyl equivalent, 175 g/eq.

(11) Ion Scavenger 1

BiO(OH)_(0.7)(NO₃)_(f)(HSiO₃)_(g)(f+g−0.3)

(12) Ion Scavenger 2

A hydrotalcite compound; DHT-4H; manufactured by KYOWA KAGAKU KOGYO Co.,Ltd.

The evaluations in the examples and in the comparative examples wereconducted in accordance with the following methods:

(1) Glass Transition Temperature

A test piece for measuring the glass transition temperature was preparedby using a transfer molding machine in the condition of 175° C., 70kg/cm² and 120 seconds. The test piece was post-cured at 175° C. for 8hours. The test piece had a dimension of 15 mm×6 mm×3 mm. Themeasurement was carried out by using an apparatus for thermomechanicalanalysis. Heat expansion of the test piece was measured while thetemperature was raised and the glass transition temperature was obtainedfrom the result of the measurement.

(2) Flame Retarding Property

A test piece having a dimension of 127 mm×12.7 mm×1.6 mm was prepared byusing a low pressure transfer machine in the condition of 175° C., 70kg/cm² and 120 seconds. After the test piece was treated at 23° C. in arelative humidity of 50% for 48 hours, the flame retarding property wasevaluated in accordance with the vertical method of UL94.

(3) High Temperatures Storage Life

Chip elements for test having a dimension of 3.0 mm×3.2 mm were sealedto 16 pDIP by using a low pressure transfer machine in the condition of175° C., 70 kg/cm² and 120 seconds and then post-cured at 175° C. for 8hours. The prepared semiconductor devices for test were kept in anatmosphere of 185° C. and electric resistance of these devices wasmeasured at a prescribed time interval at a room temperature. The totalnumber of the semiconductor device for test was 10. A device wasregarded as defective when the electric resistance increased to a valuetwice the original value. The time passed before the total number of thedefective device exceeded a half of the total number tested was regardedas the time of defect formation.

(4) Crack Resistance in Soldering

A chip element for test having a dimension of 0.9 mm×0.9 mm was sealedto 80 pQFP by using a low pressure transfer machine in the condition of175° C., 70 kg/cm² and 120 seconds and then post-cured at 175° C. for 8hours. The prepared semiconductor device was treated at 85° C. in ahumidity of 85% and formation of cracks at the surface of the treateddevice was examined by observation under the IR reflow at 240° C.

(5) Reliability in a Humid Condition

A chip element for test having a dimension of 3.0 mm×3.5 mm was sealedto 16 pDIP by using a low pressure transfer machine in the condition of175° C., 70 kg/cm² and 120 seconds. The prepared semiconductor devicefor test was subjected to the pressure cooker test at 125° C. in arelative humidity of 100%. The open defect of the circuit was measuredand the time before the open defect took place was regarded as thereliability in a humid condition.

Example 1

The following components were mixed by using a super mixer at a roomtemperature:

parts by weight Epoxy resin derived from biphenyl 23.2 YX4000K;manufactured by YUKA SHELL EPOXY Co., Ltd.; melting point, 105° C.;epoxy equivalent, 185 g/eq. Zinc molybdate 1.0 zinc molybdate coating3MgO.SiO₂; the amount of zinc molybdate coating the inorganic substanceis shown. Phenol novolak resin 13.0 softening point, 95° C.; hydroxylequivalent, 104 g/eq. 1,8-Diazabicyclo[5,4,0]undecene-7 0.8 (hereinafterabbreviated as DBU) Powder of fused spherical silica 696 averageparticle diameter, 15 μm Carbon black 2.4 Carnauba wax 2.4

The prepared mixture was kneaded by a roll at 70 to 100° C. The kneadedmixture was then cooled and pulverized to obtain a resin composition.The obtained resin composition was formed into tablets and used for theevaluation.

The resin composition had a glass transition temperature of 138° C., aflame retarding property corresponding to V-0 of the UL specificationand a high temperatures storage life of 1,200 hours. No cracks werefound on the surface of any of six samples in the test of crackresistance in soldering.

Examples 2 to 7 Comparative Examples 1 and 2

Resin compositions were prepared and evaluated by using the formulationsshown in Table 1 in accordance with the same procedures as thoseconducted in Example 4, the epoxy resin derived from hydroquinone whichis expressed by formula [7] was used as the epoxy resin. In Example 5,the epoxy resin derived from stilbene which is expressed by formula [8]was used as the epoxy resin.

The results of the evaluation are shown in Table 1.

TABLE 1 Comparative Example Example 1 2 3 4 5 6 7 1 2 epoxy resinderived from biphenyl 23.2 23.2 23.2 — — 23.2 23.2 21.7 21.7 epoxy resin1 (formula [7]) — — — 22.2 — — — — — epoxy resin 2 (formula [8]) — — — —26.4 — — — — zinc molybdate 1.0 2.0 4.0 1.0 1.0 1.0 1.0 — — ionscavenger 1 — — — — — 3.7 — — — ion scavenger 2 — — — — — — 3.7 — 3.7phenol novolak resin 13.0 13.0 13.0 13.0 13.0 13.0 13.0 13.0 13.0antimony trioxide — — — — — — — 2.2 2.2 brominated epoxy resin — — — — —— — 2.8 2.8 derived from bisphenol A DBU 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.80.8 fused spherical silica 696 696 696 696 696 696 696 696 696 (averageparticle diameter, 15 μm) carbon black 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.42.4 carnauba wax 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 glass transitiontemperature 138 139 136 131 132 137 135 134 136 flame retarding propertyV-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 high temperatures storage life 12001300 1300 1100 1000 1300 1300 300 400 (hour) crack resistance insoldering 0/6 0/6 0/6 0/6 0/6 0/6 0/6 0/6 1/6

As shown in Table 1, the epoxy resin compositions of Example 1 to 7 andComparative Example 1 and 2 all had the flame retarding propertycorresponding to V-0 of the UL specification. The epoxy resincompositions of Example 1 to 7 containing the fire retardant which wascomposed of zinc molybdate coating 3MgO·SiO₂ all showed hightemperatures storage lives of 1,000 hours or more. In contrast, theepoxy resin compositions of Comparative Examples 1 and 2 containing thefire retardant of a combination of antimony trioxide and brominatedepoxy resin derived from bisphenol A showed high temperatures storagelives as low as 300 to 400 hours.

Example 8

The following components were mixed by using a super mixer at a roomtemperature:

parts by weight Epoxy resin derived from o-cresol novolak 105 epoxyequivalent, 200 g/eq. Phenol novolak resin 55 hydroxyl equivalent, 104g/eq. 1,8-Diazabicyclo[5,4,0]undecene-7 3 (abbreviated as DBU) Fusedspherical silica 380 average particle diameter, 22 μm Fused crushedsilica 300 average particle diameter, 15 μm Fire retardant 150 zincmolybdate coating fused spherical silica having an average particlediameter of 27 μm and a specific surface area of 4.0 m²/g; 3 parts byweight of zinc molybdate per 7 parts by weight of fused sphericalsilica; (hereinafter referred to as fire retardant A) flre retardant Ahad an average particle diameter of 30 μm and the maximum particlediameter of 74 μm. Carbon black 2 Carnauba wax 5

The prepared mixture was kneaded by a roll at 70 to 100° C. The kneadedmixture was then cooled and pulverized to obtain a resin composition.

The obtained resin composition had a flame retarding propertycorresponding to V-0 of the UL specification and a reliability in ahumid condition of 500 hours.

Examples 9 to 16 and Comparative Examples 3 to 7

Resin compositions were prepared and evaluated by using the formulationsshown in Tables 2 and 3 in accordance with the same procedures as thoseconducted in Example 8. The results are shown in Tables 2 and 3.

In Comparative Example 7, fused spherical silica having an averageparticle diameter of 27 μm and a specific surface area of 4.0 m²/g wasused.

TABLE 2 Example 8 9 10 11 12 13 14 15 16 epoxy resin derived from 105 7964 — — — — — — o-cresol novolak epoxy resin 3 (formula [9]) — — — 52 — —— 52 52 epoxy resin 4 (formulae [10] + [11]]) — — — — 55 — — — — epoxyresin 5 (formula [12]) — — — — — 86 — — — epoxy resin 6 (formula [13]) —— — — — — 73 — — phenol novolak resin 55 41 — — — 34 — — — phenol resin1 (formula [14]) — — 56 48 45 — 47 48 48 DBU 3 3 3 3 3 3 3 3 3 fusedspherical silica 380 770 770 840 840 750 850 860 860 (average particlediameter, 22 μm) fused crushed silica 300 — — — — — — — — (averageparticle diameter, 15 μm) fire retardant A 150 100 100 50 50 120 20 2020 fire retardant B — — — — — — — — — ion scavenger 1 — — — — — — — 10 —ion scavenger 2 — — — — — — — — 10 carbon black 2 2 2 2 2 2 2 2 2carnauba wax 5 5 5 5 5 5 5 5 5 flame retarding property V-0 V-0 V-0 V-0V-0 V-0 V-0 V-0 V-0 reliability in a humid condition 500 500 480 450 450400 500 500 500 (hour)

TABLE 3 Comparative Example 3 4 5 6 7 epoxy resin derived from 105 79 89— 79 o-cresol novolak epoxy resin 3 (formula [9]) — — — 63 — phenolnovolak resin 55 41 51 — 41 phenol resin 1 (formula [14]) — — — 57 — DBU3 3 3 3 3 fused spherical silica 380 870 370 870 770 (average particlediameter, 22 μm) fused crushed silica 450 — 450 — — (average particlediameter, 15 μm) fused spherical silica — — — — 100 (average particlediameter, 15 μm; specific surface area, 4.0 m²/g) carbon black 2 2 2 2 2carnauba wax 5 5 5 5 5 antimony trioxide — — 20 — — brominated epoxyresin — — 10 — — derived from bisphenol A flame retarding propertyburned V-2 V-0 V-1 V-2 completely reliability in a humid 500 500 500 450500 condition (hour)

As shown in Table 2, the epoxy resin compositions of Examples 8 to 16containing fire retardant A, which was composed of fused sphericalsilica having an average particle diameter of 27 μm and a specificsurface area of 4.0 m²/g and zinc molybdate coating the fused sphericalsilica, the amount of zinc molybdate being 3 parts by weight per 7 partsby weight of the fused spherical silica, showed the excellentproperties, i.e., V-0 of the UL specification and a reliability in ahumid condition of 500 hours, although these epoxy resin compositionsdid not contain either antimony compounds or bromine compounds. Theseproperties are as excellent as those of the epoxy resin composition ofComparative Example 5 containing antimony trioxide and a brominatedepoxy resin derived from bisphenol A. In contrast, none of the epoxyresin compositions of Comparative Examples 3, 4, 6 and 7 containing nozinc molybdate satisfied the requirements of V-0 of the ULspecification.

Industrial Applicability

Semiconductor devices exhibiting excellent flame retarding property,high temperatures storage life, crack resistance in soldering andreliability in a humid condition can be obtained by sealingsemiconductor elements with the epoxy resin composition of the presentinvention.

What is claimed is:
 1. An epoxy resin composition for sealingsemiconductors which comprises (A) an epoxy resin, (B) a phenol resincuring agent, (C) a curing accelerator, (D) an inorganic filler and (E)zinc molybdate as essential components.
 2. An epoxy resin compositionfor sealing semiconductors according to claim 1, wherein zinc molybdatecoats an inorganic substance.
 3. An epoxy resin composition for sealingsemiconductors according to claim 2, wherein the inorganic substance isfused spherical silica.
 4. An epoxy resin composition for sealingsemiconductors according to claim 1, wherein the epoxy resin is acrystalline epoxy resin represented by the following formula [1], [2] or[3]:

wherein R represents hydrogen atom, a halogen atom or an alkyl grouphaving 1 to 12 carbon atoms and the plurality of R may be the same withor different from each other.
 5. An epoxy resin composition for sealingsemiconductors according to claim 2, wherein the epoxy resin is acrystalline epoxy resin represented by the following formula [1], [2] or[3]:

wherein R represents hydrogen atom, a halogen atom or an alkyl grouphaving 1 to 12 carbon atoms and the plurality of R may be the same withor different from each other.
 6. An epoxy resin composition for sealingsemiconductors according to claim, 3, wherein the epoxy resin is acrystalline epoxy resin represented by the following formula [1], [2] or[3]:

wherein R represents hydrogen atom, a halogen atom or an alkyl grouphaving 1 to 12 carbon atoms and the plurality of R may be the same withor different from each other.
 7. An epoxy resin composition for sealingsemiconductors according to claim 1, which further comprises an ionscavenger represented by one of the following formulae [4], [5] and [6]:BiO_(a)(OH)_(b)(NO₃)_(c)  [4] wherein a=0.9 to 1.1, b=0.6 to 0.8 and c=0to 0.4; BiO_(d)(OH)_(e)(NO₃)_(f)(HSiO₃)_(g)  [5] wherein d=0.9 to 1.1,e=0.6 to 0.8 and f+g=0.2 to 0.4;Mg_(h)Al_(i)(OH)_(2h+3i−2k)(CO₃)_(k)·mH₂O  [6] wherein 0<j/h≦1,0≦k/j<1.5 and m represents a positive number.
 8. An epoxy resincomposition for sealing semiconductors according to claim 2, whichfurther comprises an ion scavenger represented by one of the followingformulae [4], [5] and [6]: BiO_(a)(OH)_(b)(NO₃)_(c)  [4] wherein a=0.9to 1.1, b=0.6 to 0.8 and c=0 to 0.4;BiO_(d)(OH)_(e)(NO₃)_(f)(HSiO₃)_(g)  [5] wherein d=0.9 to 1.1, e=0.6 to0.8 and f+g=0.2 to 0.4; Mg_(h)Al_(i)(OH)_(2h+3i−2k)(CO₃)_(k)·mH₂O  [6]wherein 0<j/h≦1, 0≦k/j<1.5 and m represents a positive number.
 9. Anepoxy resin composition for sealing semiconductors according to claim 3,which further comprises an ion scavenger represented by one of thefollowing formulae [4], [5] and [6]: BiO_(a)(OH)_(b)(NO₃)_(c)  [4]wherein a=0.9 to 1.1, b=0.6 to 0.8 and c=0 to 0.4;BiO_(d)(OH)_(e)(NO₃)_(f)(HSiO₃)_(g)  [5] wherein d=0.9 to 1.1, e=0.6 to0.8 and f+g=0.2 to 0.4; Mg_(h)Al_(i)(OH)_(2h+3i−2k)(CO₃)_(k)·mH₂O  [6]wherein 0<j/h≦1, 0≦k/j<1.5 and m represents a positive number.
 10. Anepoxy resin composition for sealing semiconductors according to claim 4,which further comprises an ion scavenger represented by one of thefollowing formulae [4], [5] and [6]: BiO_(a)(OH)_(b)(NO₃)_(c)  [4]wherein a=0.9 to 1.1, b=0.6 to 0.8 and c=0 to 0.4;BiO_(d)(OH)_(e)(NO₃)_(f)(HSiO₃)_(g)  [5] wherein d=0.9 to 1.1, e=0.6 to0.8 and f+g=0.2 to 0.4; Mg_(h)Al_(i)(OH)_(2h+3i−2k)(CO₃)_(k)·mH₂O  [6]wherein 0<j/h≦1, 0≦k/j<1.5 and m represents a positive number.
 11. Anepoxy resin composition for sealing semiconductors according to claim 5,which further comprises an ion scavenger represented by one of thefollowing formulae [4], [5] and [6]: BiO_(a)(OH)_(b)(NO₃)_(c)  [4]wherein a=0.9 to 1.1, b=0.6 to 0.8 and c=0 to 0.4;BiO_(d)(OH)_(e)(NO₃)_(f)(HSiO₃)_(g)  [5] wherein d=0.9 to 1.1, e=0.6 to0.8 and f+g=0.2 to 0.4;  Mg_(h)Al_(i)(OH)_(2h+3i−2k)(CO₃)_(k)·mH₂O  [6]wherein 0<j/h≦1, 0≦k/j<1.5 and m represents a positive number.
 12. Anepoxy resin composition for sealing semiconductors according to claim 6,which further comprises an ion scavenger represented by one of thefollowing formulae [4], [5] and [6]: BiO_(a)(OH)_(b)(NO₃)_(c)  [4]wherein a=0.9 to 1.1, b=0.6 to 0.8 and c=0 to 0.4;BiO_(d)(OH)_(e)(NO₃)_(f)(HSiO₃)_(g)  [5] wherein d=0.9 to 1.1, e=0.6 to0.8 and f+g=0.2 to 0.4; Mg_(h)Al_(i)(OH)_(2h+3i−2k)(CO₃)_(k)·mH₂O  [6]wherein 0<j/h≦1, 0≦k/j<1.5 and m represents a positive number.
 13. Asemiconductor device sealed with an epoxy resin composition for sealingsemiconductors described in claim
 1. 14. A semiconductor device sealedwith an epoxy resin composition for sealing semiconductors described inclaim
 2. 15. A semiconductor device sealed with an epoxy resincomposition for sealing semiconductors described in claim
 3. 16. Asemiconductor device sealed with an epoxy resin composition for sealingsemiconductors described in claim
 4. 17. A semiconductor device sealedwith an epoxy resin composition for sealing semiconductors described inclaim
 5. 18. A semiconductor device sealed with an epoxy resincomposition for sealing semiconductors described in claim
 6. 19. Asemiconductor device sealed with an epoxy resin composition for sealingsemiconductors described in claim
 7. 20. A semiconductor device sealedwith an epoxy resin composition for sealing semiconductors described inclaim
 8. 21. A semiconductor device sealed with an epoxy resincomposition for sealing semiconductors described in claim
 9. 22. Asemiconductor device sealed with an epoxy resin composition for sealingsemiconductors described in claim
 10. 23. A semiconductor device sealedwith an epoxy resin composition for sealing semiconductors described inclaim
 11. 24. A semiconductor device sealed with an epoxy resincomposition for sealing semiconductors described in claim 12.